The present invention relates to decorative sheets and to a process for their production. In particular, it relates to a decorative sheet that offers cost savings and enhanced designability and to a process for the production of such a sheet. The decorative sheet according to the present invention is suitable for lamination over the surfaces of substrates such as steel plates, plywood laminates, aluminum plates and the like and hence is applicable, especially to household appliances, interior architectural materials, exterior architectural materials and the like, as a highly designable decorative sheet.
In recent years, luxury class household appliances, acoustic devices, room heaters, interior architectural materials, exterior architectural materials and the like have become popular. Therefore, the demand for a high level of designability, particularly, a metal-toned appearance to be imparted to decorative sheets for use in these products has arisen.
A certain method has heretofore been practiced to give a decorative sheet metallic toning in which a printing is performed on a substrate film or sheet by use of an ink containing a luster pigment such as brass, aluminum, mica, pearl or the like.
Japanese Patent Publication No. 61-51988, for instance, discloses a polyester film-covered metal sheet which is obtained by printing a pattern on an inner surface of a transparent or translucent polyester film by use of a metallic pigment-containing ink, followed by adhesion of the resulting film to a mild steel sheet or the like.
However, this conventional metal sheet is, though easily producible, disadvantageous in that the pigment is necessarily made with a small particle diameter. Consequently, there is limited irregular reflection of the light rays incident upon the pigment resulting in a printed pattern that is rather planar, less stereoscopic, less deep, deficient in metallic toning and insufficient with respect to designability.
Moreover, a decorative sheet provided with a metal sheet layer has been proposed. In Japanese Utilitly Model Laid-Open No. 63-154219, for example, a covered metal plate which is derived by laminating a metal plate with a decorative sheet having a biaxially oriented polyethylene terephthalate layer, a resin layer, a metal sheet layer, another polyethylene terephthalate layer and an amorphous polyethylene terephthalate layer superimposed one on another in the above order is disclosed.
However, despite its good metallic toning this metal plate is defective in that since it has a multi-layered structure as mentioned above, it is tedious and costly to produce.
A certain laminated sheet has also been proposed which results from lamination of a metallic pigment-containing thermoplastic resin layer with a polystyrene layer. For example, Japanese Patent Laid-Open No. 51-151742 discloses a composition derived by kneading polystyrene, ethylene-vinyl acetate copolymer, styrene-butadiene rubber and a specific type of pearl pigment, and a laminated sheet of said composition and polystyrene.
This laminated sheet has good metallic toning, but requires two different process steps to be effected: first, to prepare a composition; next, to laminate same as noted above and thus entails tedious and time-consuming procedures. Further, the pearl pigment needs to be uniformly incorporated in a large amount into, a thermoplastic resin which increases the cost.
In addition to the foregoing prior art, a metallic foil-laminated polyester film, a metal-deposited film and the like have been proposed in order to develop a metallic tone. While excelling in metallic toning, these films have a drawback in that a metal-foil layer or metal-deposited layer invites surface crazing during post-molding such as of bending or elongation of the film. The metal-deposited film has another problem in that it tends to cause a decline in adhesive strength making it insufficient at the interfacial boundary between the metal-deposited layer and the mating film.
The object of the present invention is to solve the aforementioned problems of the prior art and to provide a decorative sheet that offers low cost and excellent designability, and also to provide a process for the production of such sheet.
As a result of their intensive research, the present inventors have successfully avoided the above problems that have arisen in the prior art.
Namely, the present invention provides a decorative sheet characterized in that the sheet comprises a thermoplastic resin layer (A), an adhesive layer containing a luster pigment (B) and a transparent or translucent thermoplastic resin layer (C) laminated in the order mentioned.
The invention also provides the decorative sheet wherein the thermoplastic resin layer (A) and/or the transparent or translucent thermoplastic resin layer (C) have their respective surfaces disposed for direct contact with the adhesive layer (B) and having a pattern formed previously by printing with a printing ink.
The invention also provides the decorative sheet wherein the luster pigment has a particle diameter of 1-500 xcexcm.
Further, the present invention provides a process for producing a decorative sheet, which comprises applying a luster pigment-containing adhesive on a surface of a transparent or translucent thermoplastic resin layer (C) to form an adhesive layer (B), and subsequently laminating a thermoplastic resin layer (A) on the adhesive layer (B).
Still further, the present invention provides a process for producing a decorative sheet, which comprises applying a luster pigment-containing adhesive on a surface of a thermoplastic resin layer (A) to form an adhesive layer (B), and subsequently laminating a transparent or translucent thermoplastic resin layer (C) on the adhesive layer (B).